I had some other videos to post, but there was some malfunction...all gone. The pieces in question were by Nadja, Glen Branca, and Sunn O))).
I agree with this. To add, as DM, when you speak as an npc, have the npc directly address one PC at a time if you want to encourage that player to try speaking as his/her character. Often, if an npc addresses the entire group, the players don't feel individually invited to respond. If they are shy, they wait for the dominant player to speak up.For in character roleplaying, just talk to the PCs in-character as your NPCs and expect them to respond in-kind. Don't worry about the quality of their roleplaying, but do try giving significant NPCs one distinguishing feature such as a mannerism, accent, deep or high tone, slow or fast speech, etc.
Edit: I'd say don't put a lot of pressure on the players ("You MUST roleplay!") but do give
bonuses for well-done roleplay such as low DCs on character-interaction checks.
Also remember that roleplaying is just playing a role, determining how your character acts and thinks and what he or she says. It doesn't require you to speak in the character's voice from a first person perspective. That is acting, which is just a way to communicate roleplaying. Deciding to run behind the ruined building to avoid the green dragon's breath is just as much roleplaying as talking to an NPC in Phandalin.